Widespread implementation of prophylactic human papillomavirus (HPV) vaccines, one of which recently has become available for clinical use, could substantially decrease morbidity and mortality from cervical cancer and other HPV-related diseases. However, little is known about two factors fundamentally important to maximizing the health impact of vaccination: whether vaccination will change perceptions of risk, which may in turn impact sexual behaviors and risk for sexually transmitted infections (STI), and whether widespread virus-type-specific vaccination will affect the subsequent distribution of non-vaccine types in the population. The overall objectives of this application are to examine the impact of HPV vaccination on adolescent attitudes, sexual behaviors, STI acquisition, and HPV type distribution. The central hypotheses are that adolescent perceptions of reduced risk immediately post-vaccination will be associated subsequently with an increase in risky sexual behaviors and STI rates, and that widespread vaccination will shift the population distribution of HPV over time to non-vaccine genotypes. Guided by our preliminary data, this hypothesis will be tested by pursuing the following three specific aims: 1) Determine whether 13-17 year-old female adolescents' attitudes (e.g. risk perceptions) change as a result of HPV vaccination, whether parent and provider factors influence adolescent risk perceptions post-vaccination, and whether these risk perceptions predict subsequent sexual behaviors and STI diagnosis; 2) Explore qualitatively 11-12 year-old girls' knowledge and attitudes (e.g. risk perceptions) after HPV vaccination, whether parent and provider factors influence girls' knowledge and risk perceptions, and whether these risk perceptions influence subsequent sexual behaviors; and 3) Determine overall and type- specific HPV prevalence in a diverse sample of sexually active adolescent and young adult women, before and after widespread HPV vaccine implementation. In order to achieve the study objectives we will use the following approach. The first two aims will be addressed using longitudinal cohort studies of 11-12 year-old and 13-17 year-old girls, their mothers and their providers. The third aim will be addressed using two cross- sectional surveillance studies, before and after widespread HPV vaccination, in a diverse sample of sexually active young women. The approach is innovative, because the investigators are taking a multidisciplinary approach to understanding a previously unexplored area: the attitudinal, behavioral, and virologic impact of HPV vaccination in young women. The proposed research is significant, because the results are expected to help direct the development of evidence-based educational interventions designed to promote safe sexual behaviors after vaccination; contribute to the development of future multivalent vaccines; guide the design of post-vaccination surveillance studies of HPV epidemiology and vaccine efficacy; and create educational interventions and Pap screening recommendations that take into account shifts in viral type after vaccination. Relevance to Public Health: Examination of the attitudinal, behavioral, and virologic impact of type-specific HPV vaccination is an important but under-investigated area of behavioral science and virology that has direct implications for maximizing the public health impact of HPV vaccines. The results are expected to guide the development of evidence-based educational interventions and future multivalent HPV vaccines, both of which could maximize the effectiveness of vaccination in preventing HPV-related diseases such as cervical cancer. This application addresses several objectives of Healthy People 2010, including reducing the proportion of persons with HPV infection (objective 25-5) and reducing the death rate from cervical cancer (objective 3-4).